SOYA LECITHIN AND HUMIC SUBSTANCES IN THE BIOREMEDIATION OF A POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) CONTAMINATED SOIL

Polycyclic aromatic hydrocarbons (PAHs) are highly hydrophobic coumpounds. For this reason, historically PAH contaminated soils are often partially biotreatable as pollutants are extensively sorbed on the soil organic matter and therefore poorly available in the soil water phase where specialized microorganisms are located. The biodegradation of PAHs in such soils can be enhanced by employing surface-active agents. However, chemical surfactants are often recalcitrant and exert toxic effects towards soil biota (1). In the present research, the possibility of employing soya lecithin (SL) or humic substances (HS) as biogenic pollutant-mobilizing agents on the aerobic bioremediation of an aged-contaminated soil was investigated. A soil historically contaminated by about 13 g kg-1 of a large array of PAHs, was amended with SL or HS at 1.5% w/w and incubated in aerobic solid-phase and slurry-phase reactors for 150 days (1). A slow and partial biodegradation of low-molecular weight PAHs and a moderate depletion of the initial soil ecotoxicity were observed in the absence of agents. In the presence of the biogenic agents the overall removal of PAHs was faster and more extensive and a larger soil detoxification was detected, especially under slurry-phase conditions. SL and HS were metabolized by soil aerobic microorganisms and enhanced the presence of PAHs and of indigenous aerobic PAH-degrading bacteria in the reactor water phase. The results obtained suggest that SL and HS are non-toxic and biodegradable pollutant mobilizing agents that can significantly intensify the aerobic bioremediation of historically PAH-contaminated soils under treatment conditions similar to those employed in large-scale bioremediation (1). (1) F. Fava et al., (2004) Biotechnology & Bioengineering 88: 214-223.